Internet Service Providers are responsible for keeping people connected to their home networks. The current networking devices permit ISPs to maintain 24/7 or an uptime of 99.999% of the time. Sometimes there may be avoidable and unavoidable outages. Such as the following:

· Power outage

· Natural disaster

· Hardware failure

· Software failure

· Human error

· Process failures

· Denial-of-service (DoS) attacks

· Outages of an unknown cause


Regardless of whether an outage is avoidable or unavoidable, if it’s unplanned, it affects both raw and adjusted availability because the unplanned outage affects the overall service.